The dispensing of a plurality of liquid chemical products to one or more of a plurality of chemical receptacles is a common requirement of many industries, such as the laundry, textile and food processing industries. For example, in an industrial laundry facility, one of several operating washing machines will require, from time to time, aqueous solutions containing quantities of alkaloid, detergent, bleach, starch, softener and/or sour.
Increasingly, such industries have turned to automated methods and apparatus systems for dispensing liquid chemical products. Such automated methods and apparatus systems provide increased control of product use and minimize human contact with potentially hazardous chemicals.
The most common automatic chemical dispensing systems presently used in industry require a pump for each of the plurality of liquid chemical products. Generally, these pumps deliver raw chemical product to a dilution manifold where the chemical product is mixed with a diluent, typically water. The mixture is then pumped to a chemical product receptacle by a separate delivery pump. Such systems are relatively simple in concept, but they can be extremely expensive to build and operate. Since every chemical product storage vessel needs a separate pump to deliver it into the dilution manifold, where the number of chemical products deliverable by the system is large, capital, operating and maintenance costs can be enormous. Also, because such systems use dilution manifolds, such systems are often unacceptably slow, inaccurate and wasteful.
In U.S. Pat. No. 5,246,026, an "improved" chemical dispensing system is proposed which ostensibly requires only a single delivery pump. Chemical product is drawn from the individual chemical product storage vessels and into the dilution manifold by the delivery pump. Diluent is added to the dilution chamber and the resulting mixture is pumped via the delivery pump to the appropriate chemical receiving vessel. Such a system considerably decreases capital, operating and maintenance costs over older automated dispensing systems. However, even such an "improved" system entails continuing problems. For example, the system relies on flow monitoring devices which employ in-line flow orifices. Such orifices are inaccurate and require continuous monitoring. Also, such orifices can become plugged and are only accurate for particular viscosity ranges. To be able to handle a wide variety of materials having different viscosities, such orifices must be made adjustable. Such adjustability adds to the cost of installation and maintenance of the system. Furthermore, because the system requires a dilution manifold, the system remains relatively slow, inaccurate and wasteful. Finally, the system requires that one or both of the inputs to the dilution manifold be monitored with some form of flow indicator to properly control the resulting diluted mixture which is pumped to the chemical receiving vessel. This necessity to monitor the flow of one or more of the inputs to the dilution manifold requires the installation and maintenance of expensive flow monitoring equipment for that purpose.
Accordingly, there is a need for an automated chemical dispensing system that is faster, more reliable, less wasteful and less expensive to build, operate and maintain than prior art chemical dispensing systems.